Reaction product of a phosphorous acid with ethyleneamines, formaldehyde, and amine for flame resistance

ABSTRACT

Flame retardants, and compositions containing the flame retardants are disclosed. The flame retardants are prepared reacting ethylene diamine with polyphosphoric acid; or reacting an ethyleneamine or a mixture of ethyleneamines with phosphoric acid, polyphosphoric acid, pyrophosphoric acid, or a mixtures thereof. A 10% by weight solution of the product in water has a pH between about 3.5 to 6.5. The flame retardants are non-halogen containing flame retardants that do not gas undesirably during processing at temperatures of 235° C. or even higher.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application of PCTInternational Application PCT/US02/38855, which claims priority on U.S.Provisional Application 60/393,674, filed Jul. 3, 2002, on U.S.Provisional Application 60/359,676, filed Jan. 18, 2002, and on U.S.Provisional Application 60/340,476, filed Dec. 7, 2001.

FIELD OF INVENTION

This invention relates to flame retardants and compositions containingthese flame retardants (FR) as well as a method for the preparation ofthe flame retardants.

BACKGROUND OF INVENTION

Flame retardants that work via the mechanism of intumescence usually donot contain halogens. The flame-retardant mechanism of intumescence hasbeen reviewed. (For a review of intumescence in coatings and polymers:Don G. Brady, C. Wayne Moberly, John R. Norell, and Harold C. Walters,J. Fire Retardant Chemistry, 4, p150(1977)). The intumescent flameretardant mechanism requires an inorganic acid source, a carbon sourcesuch as a polyhydric material like dipentaerythritol, and a blowingagent, which is often an amine like urea or melamine. Optionally, ahalogen containing compound can be added for better activity. Forcoatings, the flame retardant includes the following types of compounds:a mineral acid salt such as sodium phosphate or practically waterinsoluble ammonia polyphosphate, a polyol such as starch,pentaerythritol, or dipentaerythritol, and a blowing agent such asmelamine. The standard theory is that in a fire, the heat causes themineral acid salt to decompose to form an acid, the acid dehydrates thepolyol to form char, and the blowing agent decomposes to gaseousproducts. The result is char and gas that forms a foam that is muchthicker than the original article or coating containing these flameretardants. A sequence of events with respect to formation of acid,dehydration of polyol, and release of gas must occur in the correctorder and time sequence for the gas and char to form a protective foam.Different polymers may require different ingredients or amounts ofingredients to achieve similar levels of flame retardation. It isbelieved that the polymer and the flame retardant must have similardecomposition temperatures. Thus, different mineral acid salts, polyols,or blowing agents are used in different applications and there is nouniversal recipe.

Therefore, a need exists for a single compound that performed all thetasks of the mineral acid salt, the polyol, and the blowing agent and begenerally applicable to a wide variety of polymers. Intumescence can bedifficult to achieve in practice. It is often difficult for three ormore ingredients to be well mixed in applications such as flameretarding a polymer. Good mixing of three ingredients in coatingapplications can be difficult if the ratio of solids content to solventis very high. It is much more difficult to flame retard a polymer withthree ingredients, because the above intumescence agents are added tothe polymer melt. Relatively high viscosity of the polymer melt preventseasy mixing of flame retardants to obtain a homogeneous mix and goodperformance. Mixing a melted polymer for a long time to obtain a gooddispersion of the flame retardants is unacceptable as the polymer candegrade if held above melt temperature too long. The flame resistance ofpolyolefins such as polypropylene can be improved by adding melaminepyrophosphate (MPP) and dipentaerythritol. (as taught in U.S. Pat. No.3,936,416, 1976). This patent teaches that multiple components need bemixed into the polypropylene for good flame retardant performance viaintumescence, as melamine pyrophosphate by itself requires too high aloading. Flame retardant performance will be dependent on uniformity ofmixing of the components melamine pyrophosphate and dipentaerythritolinto polypropylene. A single compound flame retardant would be easierfrom a mixing standpoint as maintaining the flame retardant in closeproximity and balance throughout would not be as crucial. For plasticsin general, it is difficult to disperse the ingredients as eachingredient may disperse differently or even agglomerate in the polymermelt.

Ethylene diamine phosphate (EDAP), which has some intumescence, is anexcellent flame retardant for olefins such as polypropylene.Unfortunately, commercial extruders process polypropylene at about 235°C. which is too high a temperature to safely use EDAP without extensiveventilation to capture ethylene diamine that is released. Thus, it wouldbe most desirable to make flame retardants that are more stable thanEDAP and which would be good flame retardants for polymers such aspolypropylene. Flame retardants such as EDAP require special conditionson commercial extruders to be used without decomposition. A flameretardant that is stable under standard processing conditions is highlydesirable.

A single compound that intumeses is discussed in PCT/US01/09514. Themost preferred examples are given as methylol melamine salts ofpolyphosphoric acid or pyrophosphoric acid. Such compounds gas duringextrusion and molding leading to undesirable mechanical properties.These compounds do not partially dissolve into the polymer duringcompounding as these compounds are not resinous in appearance orbehavior. The best practice compounds are not as effective in flameretarding olefin polymers as the compounds described herein. Examples 6and 7 of PCT/US01/09514 describe preparation of ethylene diaminereaction product with pyrophosphoric acid. The preparations used toomuch ethylene diamine and the preparations contained pyrophosphoric acidcontaminated with substantial sodium resulting in the formation of whiteparticulate that could be filtered and dried, unlike the flameretardants of the invention. The procedures in PCT/US01/09514 utilizedrying and filtering, not evaporation.

The flame retardants of the invention address the need for such a moretemperature stable flame retardant agent for olefins and other polymerswhich does not gas undesirably during processing, and which can bemachine processed at temperatures 235° C. or even higher.

SUMMARY OF INVENTION

This invention provides flame retardant compounds that provide flameretardation for a variety of applications, such as replacement of flameretardants containing halogens. The flame retardant used in manyapplications contain brominated or chlorinated compounds. There is aready market for flame retardants that do not contain halogens whichthis invention addresses.

This invention is a composition comprising:

-   a) 30 to 99.75 percent by weight of a polymeric material; and-   b) 0.25 to 70 percent by weight of a flame retardant composition    prepared by the method of:-   reacting ethylene diamine with polyphosphoric acid; or-   reacting an ethyleneamine or a mixture of ethyleneamines with an    acid selected from the group consisting of phosphoric acid,    polyphosphoric acid, pyrophosphoric acid, and mixtures thereof;

in which the ratio of the acid or acid mixture to the ethylene diamine,the ethyleneamine, or mixture of ethyleneamines is such that a 10% byweight solution of b) in water has a pH between about 3.5 to 6.5.

The flame retardant behavior of this composition can be improved byaddition of about 0.25 to 1% of anti drip agent relative to weight ofcomposition and/or 4.0 to 30% of amine selected from the groupconsisting of melamine, melamine phosphate, melamine pyrophosphate andmixtures thereof relative to weight of composition. Other amines andtheir salts are likely to be effective as well.

The flame retardant composition can be prepared by a method additionallycomprising the step of reacting the ethylene diamine, the ethyleneamine,or mixture of ethyleneamines with formaldehyde and melamine beforereacting the ethylene diamine, the ethyleneamine, or mixture ofethyleneamines with the acid or mixture of acids. Such additional stepimproves the intumescent behavior.

To improve handling behavior, the flame retardant composition can beprepared by a method additionally comprising the step of pellitizinginto particles of at least 30 microns in diameter on average and/orcoating the flame retardant composition with a water resistantthermoplastic or thermoset.

The composition can be in any form such as fiber, film, coating, orsolid object. Compositional range is complex as fibers and films areunlikely to contain particulates. Components such as anti drip agentsand melamine phosphate or melamine pyrophosphate are more useful formolded products.

Other ingredients may be added to these compositions: For example,pigments are added for color. Mica, nano-clay, chopped glass, carbonfibers, aramids, and other ingredients can be added to alter mechanicalproperties. Other flame retardants both non-halogen and halogen can beadded to form a flame retarded composition in order to capture synergiesbetween different chemistries. Anti drip agents are fluorinatedpolymeric compounds that cause polymer compositions to resist drippingwhen subjected to flame retardance testing.

It was unexpected that the flame retardant compositions intumesce whensubjected to a flame although no polyhydric component with hydroxylgroups is present, which is easily observed by subjecting flameretardant composition to propane torch. It was unexpected that the flameretardant compositions were much more stable than EDAP in that verylittle weight loss occurs at 250° C. relative to EDAP when heated in avacuum oven for 20 minutes. It was unexpected that many of the flameretardant compositions melt before decomposing. It is also unexpectedthat melting behavior enables the flame retardant compositions to easilyblend into polymers such as polypropylene and polyethylene on whatappears to be molecular dispersion as no particles are apparent, withsimilar behavior expected for other polymer groups. Molecular dispersionor very small particle dispersion apparently obtained here gives moreeffective flame retardance. It was unexpected that an apparent synergyoccurs when the flame retardant composition is added to polymers alongwith melamine or melamine phosphate. It was unexpected that addition ofan anti drip agent at 1% level improves flame retardant behavior so thatless flame retardant composition need be added. It was also unexpectedthat the composition consisting of the flame retardant composition,melamine pyrophsophate, anti drip agent and polypropylene could all beadded together at the feed throat of a twin screw extruder and obtainflame retarded polymeric composition with excellent mechanicalproperties, as addition of EDAP at the feed throat with the polymer,MPP, and anti drip agent would lead to foamed product which is highlyundesirable. The sum total of unexpected results provide a commerciallyuseful halogen free flame retarded polymeric composition.

DETAILED DESCRIPTION OF INVENTION

The composition described herein is in its most general form thereaction product of ethyleneamines, optionally an amine, and optionallyformaldehyde with phosphoric, pyrophosphoric and/or polyphosphoric acid.

Ethyleneamines are defined here as polymeric forms of ethylene diaminewith three or more nitrogen atoms and including piperazine and itsanalogues. A thorough review of ethylene diamine and ethyleneamines canbe found in the Encyclopedia of Chemical Technology, Vol 8, pgs.74–108.Ethyleneamines encompass a wide range of multifunctional, multireactivecompounds. The molecular structure can be linear, branched, cyclic, orcombinations of these. Examples of commercial ethyleneamines arediethylenetriamine (DETA), piperazine (PIP), triethylenetetramine(TETA), tetraethylenepentamine (TEPA), and pentaethylenehexamine (PEHA).Other compounds which may be applicable are, aminoethylenepiperazine,1,2-propylenediamine, 1,3-diaminopropane, iminobispropylamine,N-(2-aminoethyl)-1,3-propylenediamine, N,N′-bis-(3-aminopropyl)-ethylenediamine, dimethylaminopropylamine, andtriethylenediamine.

Certain acids are expensive to obtain in very pure form. Pyrophosphoricand polyphosphoric acid can be contaminated with orthophosphoric acidunless freshly prepared as these two acids convert to orthophosphoric inaqueous medium, with the rate being dependent on many factors such astemperature and water content. Pyrophosphoric and polyphosphoric acidcan be prepared from the appropriate pure sodium salts using the acidicion exchange resin: for example, AMBERLITE® 120H from Rohm and Haas,Philadelphia, Pa. An aqueous solution of the appropriate salt is passedthrough an ion exchange column containing AMBERLITE® 120H, at which timealmost all the sodium ions are removed leaving the pure acid. Theacidity of the prepared acid will depend on whether all the sodium ionsare removed. Thus not all the sodium must be removed to prepare theflame retardants of the invention. The most preferred for strong acidsis pH less than 1.0. Addition of ion exchange resin via a batch methoddoes not remove all the sodium ions unless repeated a few time. It ispreferred to use an ion exchange column to remove nearly all the sodiumions. The batch method is very convenient in a laboratory setting makingcompounds on a small scale, but sodium ions are less likely to beremoved.

The molar unit for pyrophosphoric acid is H₄P₂O₇. The molar unit forpolyphosphoric acid is assumed to be (HPO₃) in this work with themolecular weight assumed to be derived from (HPO₃). With there being 3or more units in a polymeric chain, the true molecular weight could bequite large as n molar units are involved with a terminal (OH) group.Such considerations are used to determine the correct reaction ratios.For all polyphosphoric acid calculations, the molecular weight will bebased on the unit (HPO₃) even though that is only an approximatemolecular weight.

Polyphosphoric acid, a commercially available form, can also be preparedby heating H₃PO₄ with sufficient phosphoric anhydride to give theresulting product, an 82–85% P₂O₅ content, as described in the MerckIndex 10^(th) edition, #7453. Such a polyphosphoric acid can be obtainedfrom Aldrich Chemical and is used in several of our examples. Metaphosphoric acid can be purchased from Aldrich Chemical, Milwaukee, Wis.and is defined as (HPO₃)_(n). The actual number of n units in apolymeric chain is not given.

Formaldehyde can be purchased as an aqueous solution, which containsstabilizers. Paraformaldehyde has been used as our source offormaldehyde in order to avoid stabilizers. Either should be a usablesource of formaldehyde.

Examples of suitable amine compounds are urea, substituted akyl ureas,thiourea, akyl thiourea, cyanamide, ethylenediurea, aniline,ethyleneamines, dicyandiamide, guanidine, guanamine, benzoguanamine,acetoguanamine, glycoluril, acrylamide, methacrylamide, melamine,benzene sulfonamide, naphthalene sulfonamide, toluene sulfonamide,ammeline, ammelide, guanazole, phenylguanazole, carbamoylguanazole,dihydroxyethyleneurea, ethyleneurea, propylene urea, melem (C₆H₆N₁₀),melam (C₆H₉N₁₁), octadecylamide, glycine, and their mixtures. Thepreferred amine is melamine.

Flame retardants are generally added to materials so that the materialpasses a particular flame retardance test. The test dictates the levelof flame retardance and thus the level of addition. Many considerationsare application dependent.

A best practice can not be formulated beforehand for all polymers.Polymers decompose at different temperatures thus requiring the flameretardant agent to be chosen with that information in hand.Polypropylene with little inherent char formation will flame retarddifferently than a polyester or a polyamide. Polymers within thesefamilies can behave very differently. Thermosets may have low processingtemperatures allowing use of flame retardant compositions that woulddecompose in an extruder. Examples have been chosen to demonstrate thebreadth of flame retardants that can be synthesized.

The reaction products of the invention especially the ones involvingpolyphosphates can be quite soluble. Thus, they are recovered byevaporation techniques. In our applications, we used a vacuum oven toremove the solvent, which is usually water. Another technique is toplace the solution containing the product on a hot plate and then use ablow dryer to blow hot air on the solution to remove the water. Thepasty product is further dried in an oven with or without vacuum. Forlarge scale production, commercially available equipment such asevaporators with scrubbers could be used. The only requirements are thatthe technique not substantially degrade the reaction product by dryingtoo long at elevated temperature and that some mixing occur as theevaporation proceeds as there is often further reaction occurring duringthe solvent removal stage.

For some applications such as thermosets or low melting polymerssubjected to temperatures substantially less than 200° C., the preferredpractice is to use EDA or DETA, the amine to be melamine, and the acidto be polyphosphate. For each mole of polyphosphoric acid, the preferredcomposition is 0.2 to 0.31 moles of melamine, at least 0.09 but lessthan 0.32 moles of formaldehyde, and at least 0.3 but less than 0.6moles of EDA or DETA. Part of the best practice is to react melamine andformaldehyde fully and then add EDA and then react with the acid. Thereaction product is extracted by evaporation as it is partially soluble.A more stable product is formed if vacuum is used during drying whichstrongly suggests a condensation occurring during vacuum drying. Theresinous type reaction product darkens as the water is extracted whichis very different behavior than the best practice reaction products ofPCT/US01/09514. This reaction product is resinous and partiallydissolves when mixed into polymer melts making it a very effective flameretardant. The resinous behavior that enables mixing readily intopolymer melts was unexpected, as compared to the best practice compoundsin PCT/US01/09514. The best practice is to prepare such resinouscompounds although our invention encompasses compounds that are notresinous. Use of DETA, TETA, and higher EDA analogues will yield morestable compounds than EDA but at additional cost. Compositions withoutmelamine are more soluble in the polymer and are more likely to formpolymeric compositions that are spinnable into fibers. Melamine additiontends to form some particulate within the resin.

The most preferred practice is to form the reaction product of DETA orTETA with polyphosphoric acid, with the polyphosphoric acid obtained viaion exchange a little more preferred. The preferred ratio of acid toethyleneamine is chosen so that the pH of the resultant flame retardantcomposition is about 3.5 to 6.5, with 4 to 6 being most preferred. Sucha product is much more stable than EDAP, as shown by heating in a vacuumoven for 30 minutes at 200° C. For flame retarding solid thermoplasticobjects, addition of compounds such as melamine, melamine phosphate, ormelamine pyrophosphate (MPP) with the DETA/polyphosphoric reactionproduct is preferred. It is preferred to add about one to three partsMPP with two parts of the DETA/polyphosphoric reaction product. Forpolypropylene, about a 30% total loading is preferred to obtain UL94 V0classification in flame retardance testing. One part MPP with two partsDETA/polyphosphoric reaction product is most preferred for flameretarded polypropylene solid objects. Another part of the best practicefor solid thermoplastic objects is to add an anti drip agent at aloading of 0.1 to 2%, with 0.25 to 1.0% most preferred.

For fiber and thin film applications the most preferred is to omit theaddition MPP and anti drip agent and simply add the DETA/polyphosphoricreaction product with appropriate processing aids to the polymer beingflame retarded.

Ethyleneamines are often made from an industrial method based onethylene and ammonia, according to Encyclopedia of Chemical Technology,Volume 8, page 82. A typical product distribution is EDA 55%, piperazine(PIP) 1.9%, DETA 23%, amino ethylpiperazine (AEP) 3.5%, TETA 9.9%, TEPA3.9%, and higher ethyleneamines 2.3%. Other methods for synthesis ofethyleneamines also give similar distributions of the ethyleneamines.All the commercial methods synthesize all ethyleneamines at same time,thus requiring separation. The least expensive method to make one of theflame retardants is to use this mixture of ethyleneamines directly orjust the fraction with a boiling point greater than EDA, for example.This will eliminate the costly step of separation and packaging ofethyleneamines into specific chemicals, which are then individuallyreacted with the acids, amines and formaldehyde. The work here showsthat it is advantageous to use the higher molecular weight ethyleneamineif higher thermal stability is desired.

The flame retardants can be added to synthetic polymers, boththermoplastic and thermoset as well as polymeric coatings and paints.The field of applicability is not limited. The applicable thermoplasticpolymers should have a melting point or substantial softening pointgreater than room temperature. Some polymers soften at temperatures wellbelow their melt point and can be processed at the softeningtemperature.

Flame retardant containing polymer compositions can be preparedconventionally in a melt mixer such as a Brabender mixer, a single screwextruder, a twin screw extruder, or any other such devise that meltspolymer and allows addition of additives. A Brabender, Buss Kneader orFarrell mixer will be preferred for polymers with poor thermal behavior.An extruder is often used for more stable polymers with high melt point.

The flame retardant containing polymer composition may contain otheradditives such as other flame retardants, standard carbon formingcompounds, and re-enforcing agents, a partial list being chopped glass,aramid fibers, talc, mica, nano-clay, or clay. Since flame retardantswork by different mechanisms, a combination of our flame retardant withother flame retardants may perform more efficiently. Other additivesinclude such ingredients as stabilizers, release agents, flow agents,dispersants, plasticizers, and pigments.

The heat treatment makes the compounds more thermally stable and canusually create a more hydrophobic surface as indicated by decreasingsolubility in water. Some applications requiring higher thermalstability or low solubility may use a flame retardant of the inventionthat has been heat treated. The preferred heat treatment is anytemperature less than 340° C. for less than 360 minutes, which includeszero minutes of heat treatment after drying. Heating with vacuum is mostpreferred. Heat treatment at temperatures less than 360° C. can be donein various methods and may include vacuum. Any method whereby the heatis applied somewhat uniformly to all the particles is important.Standard ovens and fluidized beds are other examples.

Because the flame retardants can absorb water, it may be advantageous topellitize and coat with a water insoluble coating. Such a coating withor without pellitizing will decrease water absorption and make it easierto use.

The flame retardants can be resinous depending upon the composition.These resinous flame retardants can mix into polymers and reduce theviscosity and thus the processing temperature and thereby serve asprocessing aids at low concentrations. In such situations, the lowerprocessing temperature could allow addition of other flame retardantssuch as EDAP.

The range of application of the flame retardants can be enlarged bydecreasing the particle size by milling in a monomer or solvent. Themilled compound in the monomer can then be added to the method formaking the polymers containing that monomer and thereby making apolymeric composition that comprises a flame retardant. Examples includethermoplastic and thermoset polymers such as polyesters, polyamides,polyolefins, polyurethanes, and their co-polymers. Thermosets forelectronic packaging are often prepared from a solvent solution with thesolvent being organics such as the ketones (methylethyl ketone).Electronic packaging involves multilayer films and adhesives, with thetotal package required to pass particular flame retardant tests. Ourflame retardants milled a solvent, where the flame retardant isinsoluble, could be added to the thermoset solution and then cured instandard fashion.

The classes of polymers to which the flame retardants are applicableinclude the following: acrylic, butyl, cellulosics, epoxy, furan,melarnine, neoprene, nitrile, nitrocellulose, phenolic, polyamide,polyester, polyether, polyolefin, polysulfide, polyurethane, polyvinylbutyral, silicone, styrene-butadiene, butyl rubber, and vinyl.

Polymer and polymer compositions to which the flame retardants of theinvention are applicable to include the following:

-   1. Mono and diolefins such as polypropylene (PP), thermoplastic    olefins (TPO), polyisobutylene, polymethylpentene, polyisoprene,    polybutadiene, polyethylene with or without crosslinking,    highdensity polyethylene, low density polyethylene, or mixtures of    these polymers. Copolymers of mono and diolefins including other    vinyl momomers such as ethylene-propylene copolymers, ethylene-vinyl    acetate copolymers. Terpolymers of ethylene with propylene and a    diene such as hexadiene, cyclopentadiene or ethylidiene norborene    and vinyl monomers such as vinyl acetate. Mixtures of polymers under    1.-   2. Polystyrene, poly p methyl styrene, poly α methylstyrene, and    copolymers of styrene or α methylstyrene with dienes or acryl    derivatives such as styrene-butadiene, styrene-actrylonitrile,    styrene-alkylmethylacrylate, styrene-butadiene-akylacrylate,    styrene-maleic anhydride, and styrene-acrylonitrile-methylacrylate.-   3. Polyphenylene oxide and polyphenylene sulfide and their mixtures    with styrene polymers or with polyamides.-   4. Polyurethanes derived from polyethers, polyesters and    polybutadiene with terminal hydroxy groups on one hand and aliphatic    or aromatic polyisocyanates on the other as well as their    precursors.-   5. Polyamides and copolymers derived from diamines and dicarboxylic    acids and/or from aminocarboxylic acids or the corresponding    lactams, such as polyamide 4, polyamide 6, polyamide 6/6, 6/10,    6/12, 4/6, 66/6, 6/66, polyamide 11, polyamide 12, aromatic    polyamides based on aromatic diamine and adipic acid: and iso-    and/or terephthalic acid and optionally an elastomer as modifier,    for example poly-2,4-trimethyl hexamethylene terephthalamide, poly m    phenylene-isophthalamide.-   6. Polyesters derived from dicarboxylic acids and dialcohols and/or    from hydrocarboxylic acids or the corresponding lactones such as    polyethylene terephthalate, polybutylene terephthalate, polyethylene    terephthalate/polybutylene terephthalate mixtures, polyethylene    terephthalate/polybutylene terephthalate copolymers, poyl    1,4-dimethyl clclohexane terephthalate, polyhydroxybenzoates, and    co-polymers with ethylene.-   7. Polyvinyl chloride and copolymers with ethylene, copolymers of    tetra fluro ethylene and ethylene.-   8. Thermoset polymers include for example unsaturated polyester    resins, saturated polyesters, alkyd resins, amino resins, phenol    resins, epoxy resins, diallyl phthalate resins, as well as    polyacrylates and polyethers containing one or more of these    polymers and a crosslinking agent. A review of thermosets is found    in Ullmann's Encyclopedia of Industrial Chemistry, Vol A26, p 665-   9. Polymers for insulation such as fluorinated ethylene-propylene    (FEP), cross linked polyethylene (XLPE), ethylene-propylene rubber    (EPR), tree cross linked polyethylene (TRXLPE), and ethylene vinyl    acetate (EVA).-   10. Cellulose acetate, flexible polyurethane, rigid polyurethane.-   11. Fluoropolymers and co-polymers such as TEFZEL®, DuPont Co,    Wilmington, Del. Elastomers such as spandex as defined in    Encyclopedia of Chemical Technology. Polyimides such as KAPTON®,    DuPont Co., Wilmington, Del. And defined in Encyclopedia of Chemical    Technology.-   12. Polyethylene and its co-polymers.-   13. Ethylene vinyl acetate, ethylene vinyl acetate carbon monoxide    and ethylene n butyl acrylate carbon monoxide and ethylene n butyl    acrylate glycidyl methacrylate, ethylene methyl, ethyl, and butyl    acrylate ethylene (methyl, ethyl, buthyl)    acrylate-vinyltrimethylsilane, or vinyltriethylsilane ethylene    methyl acrylate and ethylene methyl acrylate MAME, ethylene acrylic    and methacrylic acid, ethylene acrylic and methacrylic acid ionomers    (Zn, Na, Li, Mg), maleic anhydride grafted polymers.

Melamine pyrophosphate and mono, di-, or tri-pentaerythritol arecommonly used together (see U.S. Pat. No. 3,914,193) with a film forminglatex of a poly(vinyl ester) to form an intumescent latex coatingcomposition or intumescent paint or could be used to make latex backingfor carpets. Such latex's can be in aqueous or alcohol mediums. Animprovement is to use the self intumescing reaction products of theinvention with the latex binder to form coatings or paints that areflame retardant coatings. A usable coating can contain one or more ofthe other ingredients such as potassium tripolyphosphate, ethhoxylatedcastor oil, waxy-fatty ester de-foamer, chlorinated paraffin, TiO₂, andhydroxy ethyl cellulose which are normally ingredients in flameretardant paints. One skilled in the art of coatings can easily add thecorrect combinations to get proper physical behavior of a coating orcarpet backing with the compounds of the invention.

The materials of the invention have value for flame retarding articles,films, and fibers.

Abbreviations Used in Examples

Mel—melamine, PF—paraformaldehyde, ID#—sample identification,PA—phosphoric acid of 85% concentration, meta—metaphosphoric acid,SAPP—sodium acid pyrophosphate, HEX—sodium polyphosphoric acid,teta—triethylene tetramine, deta—diethylene triamine, eda—ethylenediamine, EDA123 is equal parts EDA, DETA, TETA. Dicy is dicyandiamide.POPP is polyphosphoric acid from Aldrich Chemical.

Sources of Materials:

Melamine was obtained from DSM Corp., Saddlebrook, N.J.

PCS Inc., Newark, N.J. for 85% concentration phosphoric acid.

Paraformaldehyde, meta-phosphoric acid, polyphosphoric acid, sodium acidpyrophosphate, sodium polyphosphoric acid, DETA, TETA, and EDA wereobtained from Aldrich Chemical, Milwauke, Wis.

CYMEL® resins were obtained from Cytek Industries, West Patterson, N.J.

FR150 from Shamrock Technology, Newark, N.J.

EXAMPLES

All of the ingredients for the examples demonstrating some of thereaction products of the invention are listed in first nine tables ingrams and a similar experimental procedure was usually followed.Abbreviations used in the table are listed above. The first entry in thetables is always the sample ID. The amount in grams of the amine,paraformaldehyde, water, ethyleneamine, and phosphoric acid (85%concentration) are the first five entries after the sample designation.Step 1 was to prepare methylolated amine by heating the amine,paraformaldehyde, and water to a temperature near boiling. The amountsof these ingredients and temperature were chosen so that a clearsolution was obtained and as concentrated as practically possible. Thesecond step was to add the EDA or ethyleneamine to the hot methylolamine solution. The resultant solution was then added to the phosphoricacid rapidly to form a resinous final product. Nearly all the tableshave a column labeled foam which designates the level of intumescentchar that forms when heated in an oven at 500° C. The pH of a 10%aqueous dispersion/solution was listed in the last column for somesamples.

A typical demonstration is sample 24c in Table I. First, 3.15 g ofmelamine, 2.5 g of paraformaldehyde, and 3.15 g of water was mixed in aglass beaker and then heated to boiling for a few minutes with formationof a clear solution of methylolated melamine. Then, 3.8 g ofdiethylenetriamine (DETA) was added drop wise. Strong bubbling occurredand some reaction was obvious. The methylolated melamine-DETA solutionwas added quickly with vigorous stirring to 11.4 g of phosphoric acid85%. This was done before the methylolated melamine-DETA solutionstarted to precipitate. An orange colored solution formed with muchbubbling which turned into a solid mass which is obviously a resinousmaterial. The yield of solid mass was about 20.2 g, whereas the weightof the initial ingredients was about 24 g.

Numerous samples are shown in Table I prepared in similar fashion. Itappears desirable to run the reaction with as little water as possibleso as to enable easier drying. Samples 8c and 9c in Table I were run asabove except for the absence of methylol melamine. The product was verydifferent in that it has the form of crumbs, not a resin. The color wasalso very different in that it was not a shade of orange. It appearsthat the DETA salt of phosphoric acid was prepared as expected and is acompound of the invention. Its intumescence was less as compared tosample 24c.

TABLE I The reaction product of diethylenetriamine and methylol melaminewith phosphoric acid 85%. initial int ID# Mel PF H2O DETA PA weightyield char pH  8c 0 0 0 7.6 8.5  9c 0 0 0 3.8 8.5 5.38 10c 3.15 1 15 3.88.5 5.9 11c 3.15 2 5.4 3.8 8.5 12c 3.15 2 5.4 3.8 8.5 13c 3.15 3 5.4 3.88.5 13c-b 3.15 3 5.4 3.8 8.5 14c 3.15 3 4.1 3.8 8.5 15c 3.15 2.5 4.1 3.88.5 16c 3.15 2.5 4.1 3.8 8.5 16c-b 3.15 2.5 4.1 3.8 3.04 17c 3.15 2.54.1 0 3 18c 3.15 2.5 4.1 3.8 10 3.92 19c 3.15 2.5 4.1 3.8 11.4 3.64 20c3.15 2.5 4.1 7.6 11.4 21c 3.15 3 4.1 3.8 11.4 25.5 21.5 good 22c 3.15 24.1 3.8 11.4 24.5 20.8 good 23c 3.15 2.5 4.1 3.8 11.4 25 21.4 good 24c3.15 2.5 3.15 3.8 11.4 24 20.2 good 25c 3.15 3 6.1 3.8 11.4 27.5 22.2good

Flame retardant capability of sample 24c was tested by mixing withpowdered polyethylene, a polymer known to be difficult to flame retardbecause of its negligible char. Sample 24c and powdered polyethylenewere ground together with a mortar and pestle at a ratio of 35% sample24c, 65% polyethylene. The mixture was then mixed on a hot plate set at235° C. with two spatula's for about 5 minutes. The melted mass wasshaped into a film about 0.24 inches thick. The film was subjected to asmall BIC® cigarette lighter for 60 seconds, the film held verticallyand the flame applied at the bottom. The polyethylene film extinguishedwithin a few seconds after the flame was removed with no dripping,indicating that sample 24c is a very effective flame retardant. Nodripping indicates strong charring. A comparable control sample madefrom polyethylene polymer burns substantially and drips when subjectedto same flame for 60 seconds. Similar results were found for othersamples prepared with 21C, 22c, 23c, and 25c from Table I. Samples 8cand 9c have flame retardant activity but appear to flame a longer timeand there was some undesirable dripping when the flame is applied for 60seconds.

Ethylene diamine (EDA) has a lower boiling point than DETA. In Table II,the reaction products of EDA and methylol melamine with phosphoric acid85% are shown. The same procedure as in Table I was followed. Firstmethylol melamine was formed, then EDA was added. Next, the EDA/methylolmelamine was added to phosphoric acid rapidly. A resinous mass formedwith orange like color. The flame retardant characteristics wereinvestigated as with sample 24c above. Sample 2e was dried, ground, thenadded to powdered polyethylene via heating on a hot plate at 35%loading. The flame retarded polyethylene when subjected to a cigarettelighter flame for 60 seconds extinguished shortly after the flame wasremoved and did not drip. Considerable charring was observed. A controlsample burns substantially after the flame is removed and drips whilethe flame is applied.

A similar experiment was repeated with sample 1e except the polymer wasethylene vinyl acetate (EVA) co-polymer, that contains 18% vinyl acetatemonomer and melts at about 90° C. The flame retarded polymer stoppedburning shortly after the flame was removed with good charring asobserved above with polyethylene. A control EVA was fully ignited by thesame 60 second burn with much dripping.

TABLE II The reaction product of ethylene diamine and methylol melaminewith phosphoric acid. initial Mel PF H2O EDA PA yield weight char 1e3.15 2.5 4 3.8 11.4 19.7 24.9 good 2e 3.15 2.5 4 2.5 11.4 18.8 23.6 good

Flame retardants similar to that of Table I and Table II can be moreeasily prepared by utilizing commercially prepared methylol melamineresins from Cytek Industries, West Patterson, N.J., the trade name beingCYMEL®. The advantage of these resins is that the concentration is muchhigher at about 80%, less water or solvent to remove, and the CYMEL®resins are partially methylated so that stability is not an issue. Themethylol melamines used in Table I and Table II will precipitate ifcooled and allowed to stand, a disadvantage compared to the CYMEL®resins. In Table III, the resins used are CYMEL® 373 and CYMEL® 385which are aqueous based. Numerous solvent based CYMEL® resins areavailable and would be suitable as well. All the samples in Table IIIwere prepared by adding DETA drop wise to the appropriate amount ofCYMEL® 373 or CYMEL® 385 and heating to about 85° C.–100° C. Thissolution was then added rapidly to the appropriate amount of phosphoricacid that had been also heated to about 85° C. The reaction rate wasslower than that found for the preparations in Table I, but the finalproduct appears to be the same resinous mass. A sample was tested forflame retardance by mixing into powdered polyethylene on a hot plate,following procedures outlined above. Good flame retardant behavior wasobserved as with sample 24c above for both CYMEL® resins.

TABLE III The reaction product of Cytek methylol melamine resins withDETA and phosphoric acid. Sample # CYMEL ® DETA PA Char pH  5b-373 7 0 05.2 0 8.9 0 0 0  6b-373 7.28 0 0 5.27 0 8.7 0 0 0  7b-373 7.53 0 0 5.240 8.79 0 0 0  8b-373 7.13 0 0 5.36 0 8.59 0 0 0  9b-373 8.3 0 0 4.04 08.78 0 0 4.2 4.2 10b-373 4.5 0 0 6 0 8.75 0 0 0 11b-373 4.5 0 0 3.8 08.5 0 0 4.9 4.8  2b-385 9.5 0 0 5.2 0 8.5 0 0 0  3b-385 9.5 0 0 5.2 08.5 0 0 0  1b-385 3.15 1 0 5.2 0 8.5 0 0 0

A different type of product results if methylolated ethyleneamine wasmixed with ethyleneamine, which was then added rapidly to phosphoricacid. The reaction product was not a salt but a resin. In Table IV, thereaction products of DETA and methylol DETA with phosphoric acid areshown. The same procedure as in Table I was followed. First methylolDETA was formed by adding PF to DETA which may or may not contain water.Then DETA was added to the methylolated DETA. Next, the DETA/methylolDETA was added to phosphoric acid rapidly. A resinous mass formed withorange like color after the remaining water was extracted from thereaction product. The reaction product pours if heated. This compound isnecessarily a flame retardant as it contains phosphates and amines. Thisflame retardant could have advantages in applications where a viscousmaterial is necessary as the flame retardant.

TABLE IV The reaction product of methylolated DETA and DETA withphosphoric acid. DEta PF H2O DETA PA char 26c 1 2 1.15 2.8 8.4 good 27c1 1.3 0 2.84 8.4 good 28c 1 0.8 0 2.8 8.4 good

In Table V, a scheme is presented by which compositions are chosen.CYMEL® 385 is about 80% resin, with about 3.2 formaldehyde molecules permelamine to estimate it's molecular weight. The ingredients CYMEL®,phosphoric acid (pa), and DETA or TETA have been chosen to obtain thenominal compositions shown in the table. Example 385-d6 has ingredientschosen so that the composition is 1 molecule of mp per one molecule ofDETA-pa1.8. Example 385-t2 has 1.5 molecules of mp per one molecule ofTETA-pa2. The pH of the resultant resin products are also shown. Thesechoices of composition appear to give good color and flame retardantproperties when mixed into ethylene vinyl acetate, as compared to lesssystematic choices in tables above.

TABLE V Reaction product of CYMEL ® 385 and DETA or TETA with phosphoricacid. CYMEL ® - 385 pa composition pH DETA 385-d6 7.07 2.88 2.57mp:dp1.8 3 385-d7 7.07 2.88 3.86 mp:1.5(dp1.8) 3.4 385-d8 7.07 2.88 5.15mp:2(dp1.8) 385-d9 7.07 2.88 2.57 mp:dp1.6 3.04 385-d10 7.07 2.88 3.86mp:1.5(dp1.6) 3.66 385-d11 7.07 2.88 5.15 mp:2(dp1.6) 4.67 TETA 385-t17.07 2.88 3.65 mp:tp2 2.8 385-t2 10.60 4.32 3.65 1.5(mp):tp2 3 385-t314.14 5.76 3.65 2(mp):tp2 385-t4 7.07 2.88 5.48 mp:1.5(tp2) 3.9 385-t57.07 2.88 7.31 mp:2(tp2) 5

A simple test of intumescense is to heat approximately 0.5 g of a flameretardant in an oven at about 500° C. for about two minutes. Samples24c, 1e, and 2e were found to form a foam that is at least 50 timeslarger than the original material when heated at 500° C. Samples 26c,27c, and 28c foam about one half as much as samples 24c, 1e, and 2e whenheated at 500° C. Actual tests would be needed to determine which flameretardant was the most effective for a given situation. The intumescenteffect is only one of the important factors in determining theefficiency of flame retardants.

Next, experimental data is presented on the preparation of ethyleneaminephosphates which have stability superior to that of ethylene diaminephosphate (EDAP). The most stable product was obtained by the reactionof polyphosphoric acid (popp) with EDA, DETA, or TETA. Severalexperiments are summarized in Table VI along with the pH and the weightloss at 300° C. All experiments follow the same procedure. For example,Popp-E2 was prepared by first heating 24 g of popp so that it stirseasily. Then, 18 grams of EDA was added and stirred in rapidly. Much ofthe EDA was vaporized. Enough EDA was reacted to give the reactionproduct with various pH values depending on how rapidly the EDA wasadded. A similar procedure was followed for reaction of popp with DETAand TETA.

These compounds could have excellent flame retardant properties becauseof good thermal stability. On a hotplate at 200° C., ethylene vinylacetate and sample popp-E2 were mixed at a 35% loading. A film of thismixture did not sustain burning when ignited with a cigarette lighter.

TABLE VI The reaction product of EDA, DETA, and TETA with polyphosphoricacid (popp). popp pH TGA EDA Popp-E1 4.5 6 weight loss at 300° C. lessthan 1% Popp-E2 18 24 2.02 weight loss at 300° C. less than 1% Popp-E34.6 6.2 5.73 weight loss at 300° C. less than 6% Popp-E4 4.95 6 5.52Popp-E5 4.3 6.15 3.88 Popp-E6 4.5 6 DETA Popp-E1 5.15 8 weight loss at300° C. less than 3% Popp-D2 5.15 8 Popp-D3 5.66 8 Popp-D4 6.18 8Popp-D5 5.15 8 TETA Popp-T1 3.65 6 2.2 weight loss at 300° C. less than3% Popp-T2 4.01 6 Popp-T3 4.38 6 Popp-T4 3.65 6

Polyphosphoric acid is quite expensive compared to sodium polyphosphate,available from Tilley Chemical Corp., Baltimore, Md. Polyphosphoric acidcan be made by dissolving sodium polyphosphate in water and thenextracting the sodium ions with an ion-exchange resin (AMBERLITE® 120from Aldrich Chemical) to form polyphosphoric acid.

In Table VII, the reaction of ethyleneamines with polyphosphoric acidwas found. The polyphosphoric acid was prepared by adding 223 g of ionexchange resin AMBERLITE® 120, 103 g of water, and 50 g of sodiumpolyphosphate to a beaker and then heating and stirring for about 10minutes at which time the pH of resultant acid was about 0.9. Next, theresin was filtered, then washed with about 43 g of water and filteredand collected with the acid. About 178 g of acid was collected. For theexperiments in Table VII, about 30 g of acid was put in a beaker thatwas heated and stirred. Then EDA was added to the desired pH. Four runswere made and the pH's were 7.86, 5.63, 5.56, and 6.14 in Table VII. Theproduct was obtained by placing the solution in a vac oven at about 85°C. to extract the water and obtain the product. Similar procedure wasfollowed for DETA (samples poly-D1, Poly-D2) and TETA (Poly-T1). The pHof the products are shown in the table. Good flame retardant behaviorwas assured because of high phosphorous content and good thermalstability. Loading by weight of 35% in ethylene vinyl acetate showedvery good flame resistance. The method of removing sodium ions is notvery good when using a batch method and the solution is quiteconcentrated.

TABLE VII Reaction Product of Ethyleneamines with Poly-Phosphoric acid.pH- pH- 50 g sapp, 103 h2o, 43wash, solution product 223ixr pH = .9Poly-E1 7.86 EDA add 5.6 Poly-E2 5.63 EDA add 5 weight loss at 300° C.less than 6% Poly-E3 5.56 EDA add 4.83 weight loss at 300° C. less than4% Poly-E4 6.14 EDA add 5.18 Poly-D1 5.35 DETA 4.36 add Poly-D2 5.45DETA 5.1 weight loss at 300° C. less than 5% add Poly-T1 5 TETA 3.9 add

Instead of using an ion exchange resin to prepare polyphosphoric acid,polyphosphoric acid from Aldrich chemical was reacted withethyleneamines. For the examples in Table VIII, water (listed in grams)was mixed with an equal weight of polyphosphoric acid. EDA andethyleneamines (deta, or teta) was added slowly to the popp solutionuntil a pH approximately between 4 and 7 is reached. Values of pHoutside this range would be suitable for situations that high acidity orbasicity was allowable. The solution was then dried in a vacuum oven andthe pH of 10% solutions is given in Table VIII. These compounds areshown to be more stable than edap when heated in an oven set at 250° C.The samples 1,2, and 3 loose weight much less rapidly than EDAP. Samples1,2, and 3 were also mixed on a hot plate set 230° C. with polypropyleneat a 35% concentration. Films prepared in such a manner were resistantto burning. Thus, compounds such as 1,2 and 3 have the requirements of asuitable flame retardant for olefins. Such salts are expected to havebetter flame retardant performance as the greater phosphoric contentwill give improved charring properties.

TABLE VIII Reaction Product of Ethyleneamines with Polyphosphoric acid.pH 10% popp H2O concern. 1 teta 26 26 5.5 2 deta 27 27 5.6 3 eda 29 296.3

In examples in previous tables, ethyleneamine reacted directly with 85%concentration reacted very vigorously which might be undesirable as someethyleneamine may be vaporizing. In Table IX, water was added to the 85%phosphoric acid (PA) and then ethyleneamine was added slowly to theresultant acid. The amine was added so that the pH is in the range of4–7, but pH outside this range is acceptable. The samples were dried ina vacuum oven and the pH of the resultant product are shown. The samples5 and 6 were also more stable than EDAP when heated in an oven at 250°C. Films prepared by mixing samples 5 and 6 with polypropylene on a hotplate at a 35% concentration had good flame retardant properties.

TABLE IX Reaction Product of Ethyleneamines with Phosphoric acid (allentries in grams). PH 10% amine H2O PA concern. 5 teta 19.26 32 30 6.2 6deta 14.5 30 30 5.89

Polyphosphoric acid with little sodium was prepared by running asolution of sodium polyphosphate through an ion exchange column so thatnearly all the sodium ions are removed. Specifically, the columncontained 250 ml of ion exchange resin, AMBERLITE® 120 from Rhom andHaas, Philadelphia, Pa. The solution was prepared by dissolving 30 g ofsodium polyphosphate in about 165 g water with a little heat which wasthen fed through the column and the polyphosphoric acid collected. Thecolumn was operated in standard fashion. EDA was then reacted with thepolyphosphoric acid until a pH of 4 to 8 is attained. About 9 g of EDAwas reacted with the polyphosphoric acid to obtain the desired pH. Thedilute EDA-polyphosphoric acid solution was then dried in a vac oven atabout 100° C. to yield about 33 g of product (example Polyp-EDA).Pa-teta was prepared according to procedure for Table IX. Ppa 7R hex(1-2-3) was prepared by reacting freshly prepared polyphosphoric acidwith a mixture of equal parts of EDA, DETA, and TETA, until a pH between4–8 is obtained.

Sample ppa 10L EDA DICY was prepared by adding 1 g of dicyandiamide tofreshly prepared polyphosphoric and then adding EDA until a pH of about5.8 was obtained. Vacuum oven drying was used to extract the product.

All of our new compositions have stability at 250° C. that are muchbetter than EDAP. This overcomes a major limitation of EDAP.Polyphosphoric acid-EDA yields a product that is more stable and thuspreferable to EDAP. The phosphorous content of polyphosphoric acid-EDAcompounds was also higher than that of EDAP which should lead to moreefficient FR, provided all other things are the same. The reaction ofTETA, which is a higher molecular weight EDA, with phosphoric acid(Pa-teta) also gives a higher stability product than EDAP and will leadto the desired goal of higher processing temperature.

The next set of runs (see Table X) were the result of interactingmelamine, EDA, and formaldehyde in water and then adding topolyphosphoric acid in water. The polyphosphoric acid was prepared withan ion exchange column. First, about 60.3 g of sodium polyphosphate wasdissolved in about 350 ml of water. The solution was then passed throughan ion exchange column containing about 550 ml of AMBERLITE® 120 ionexchange resin to extract nearly all the sodium and form polyphosphoricacid. Water was used to purge the remaining polyphosphoric acid in thecolumn. The yield of polyphosphoric acid in water was about 700 ml, withthe actual polyphosphoric acid content about 48 g. In a second beaker,approximately 10 to 20 g of melamine, 2 to 3.5 g of paraformaldehyde,and about 16 g of EDA were added to 88 g of water. This was heated withstirring for about 10 minutes to a temperature less than or equal toboiling for full reaction. The amine solution was quickly added to thepolyphosphoric acid solution with stirring and subsequent heating for afew minutes. The pH of the final mixture was adjusted to a pH from 4 to7 which usually required addition of one to two grams of EDA. Themixture was placed on a hot plate and standard portable blow dryers wereused to evaporate the water leaving a pasty mixture. The pasty mixturewas placed in an oven to remove all water and giving a resinous productthat darkens as it dries. The darkening of the product as the finalmoisture is removed is indicative of becoming a new composition that isobtained by the evaporation method. The resinous product breaks intopieces which can then be mixed into polymer melts via standardtechniques: extruders, Brabenders, Buss kneaders, etc. This productpartially dissolves when mixed into polymer melts resulting in veryefficient flame retardance and good mechanical properties as compared toEDAP.

TABLE X Reaction product of melamine, paraformaldehyde, and EDApre-reacted in water and then added to polyphosphoric acid in water(entries in grams). ID# M PF EDA H2O Hex 1 14 3.5 18 88 60.3 2 15 3 17.388 60.2 3 13 3 17.3 88 60.3 4 11 3 17.3 88 60.3 5 12 3.5 18 88 60.3 6 122.5 16.8 88 60.2 7 12 3 18 88 60.3 8 10 3 17 88 60.2 9 14 3 17.7 88 60.310 20 2 17.6 88 60.3 11 14 2 18 88 60.2

The pH of the samples of Table X are about 4–7. As a particular example,use a Brabender to prepare a small sample. Set the Brabender at atemperature of 240° C. Add 36 g of standard extrusion gradepolypropylene and mix for about 1.5 minutes until the polymer is melted.Then add 18 g of sample #1 from Table X and mix for 5 to 7 minutes. Makeresultant product into bars ⅛ inch thick, 6 inch long, and 0.5 inchwide. The samples pass UL94 testing with a V0 rating.

Similar reactions can be made with pyrophosphoric acid and phosphoricacid. Sodium acid pyrophosphate, 60.5 g, was dissolved in 450 g of waterand run through an ion exchange column to prepare pyrophosphoric acid.Separately, 14 g of melamine and 3 grams of paraformaldehyde was addedto 88 g of water and heat for about 10 minutes to a temperature of 60°C. to 80° C. Then, 17 g of ethylene diamine was added to the melamine/pfsolution and continued heating to get full reaction. Then, this basicsolution was added to the pyrophosphoric acid and mixed with continuedheating. About 1 g of EDA was added to adjust pH to about 5. Water wasevaporated to extract the final product, which appeared to be resinousand darkened as vacuum dried.

For comparison, the EDA salt of pyrophosphoric acid was prepared.Pyrophosphoric acid was prepared as above by running a solution ofsodium pyrophosphate through an ion exchange column. Then, 25 g of EDAwas added to about 25 g of water and stirred. The EDA/water was addedrapidly to the pyrophosphoric acid and heated to about 60° C. The waterwas evaporated to extract the product, which appeared to be crystallineand much easier to dry than the other compound of pyrophosphoric acidjust prepared which contained formaldehyde.

Finally, a similar salt of phosphoric acid was prepared. First, 14 g ofmelamine and 3 grams of paraformaldehyde were added to 88 g of water andheated for about 10 minutes to a temperature of 60° C. to 80° C. Then,17 g of ethylene diamine was added to the melamine/pf solution andcontinued heating to get full reaction. Then, this basic solution wasadded to 42 g of 85% concentration phosphoric acid and mixed withcontinued heating. The water was evaporated to extract the product,which seemed a mixture of crystalline-like and resinous-likeconsistency.

The preferred composition for applications requiring extrusion have beenscaled up in a 22 L column. First, 2640 g of sodium polyphosphate wasdissolved in 15.4 L of water. The solution was processed through the ionexchange column to obtain polyphosphoric acid. Separately, 616 g ofmelamine and 132 g of paraformaldehyde were added to 3872 g of waterwith heating and stirring to about 60° C. to 80° C. Then 748 g of EDAwas added to 800 g of water and let react for few minutes. Next, theEDA/water was added to the melamine/pf mixture and heating continued tofully react. Next, the amine mixture was added to the polyphosphoricacid solution rapidly with stirring. The water was evaporated to yield aresinous, pasty product which was further dried in a vacuum oven. Next,the product was mixed with polypropylene pellets at a loading of 30% byweight. The mixture was compounded in a 25 mm Werner and Pfleiderer twinscrew extruder with the barrel temperatures set at 180° C. and screwspeed of 150 rps. The mixture was added to the extruder at the main feedthroat to demonstrate good thermal behavior, especially as the extruderhad a standard screw design to melt and mix the composition. Theresultant composition is molded into tensile bars ⅛ inch thick and flexbars 1/16 inch thick. The bars have elongation greater than 15% and theflex bars pass UL94 testing with a V0 rating.

Another preferred composition for applications requiring extrusion wasmade with the 22 L column. First, 2640 g of sodium polyphosphate wasdissolved in 15.4 L of water. The solution was processed through the ionexchange column to obtain polyphosphoric acid. The polyphosphoric acidsolution was divided into three equal parts. Sample 5-1 was prepared byadding 320 ml of TETA to one third of the polyphosphoric acid solution.Sample 5-2 was prepared by adding 320 ml of DETA to one third of thepolyphosphoric acid solution. Sample 5-3 was prepared by adding 200 mlof EDA and 100 ml of TETA to one third of the polyphosphoric acidsolution. The water was evaporated for all three samples to yield aresinous, pasty products which were further dried in a vacuum oven. Allthree samples were found to be much more stable that EDAP when heated ina vacuum oven. The three samples all show substantial intumescense whenheated with a propane torch.

A composition for extrusion was prepared by mixing together by weight70% polypropylene pellets, 20% sample 5-2, and 10% melaminepyrophosphate. The mixture was compounded in a 25 mm Werner andPfleiderer twin screw extruder with the barrel temperatures set at 180°C. and screw speed of 150 rps. The mixture was added to the extruder atthe main feed throat to demonstrate good thermal behavior, especially asthe extruder had a standard screw design to melt and mix thecomposition. The resultant composition is molded into tensile bars ⅛inch thick and flex bars 1/16 inch thick. The bars have elongation ofabout 6% and the flex bars pass UL94 testing with a V0 rating. Thepresence of MPP apparently makes molding good quality bars easier.

Another composition was prepared by mixing together by weight 69%polypropylene pellets, 20% sample 5-2, 10% melamine, and 1% FR150. Thesame procedure was followed on 25 mm twin screw extruder. Molded barsgave an elongation of about 10% and the bars pass UL94 testing with arating of V0 at 1/16 inch thickness. The presence of melamine also makesmolding good quality bars easier.

Sodium polyphosphate, 60.5 g, was dissolved in 350 g of water. An ionexchange column was used to prepare polyphosphoric acid which was heatedfor about 10 minutes to a temperature of 60° C. to 80° C. Next, 26 g oftetra-ethylene pentamine (TEPA) was added to the polyphosphoric acid andmixed with continued heating. Water was evaporated to extract the finalproduct, which appears to be resinous and transparent yellow color. Whenheated in a vacuum oven at 200° C., this product of polyphosphoric acidand TEPA is much more stable than EDAP.

The next examples of making the flame retardant compositions werecarried out by addition of polyphosphoric acid from Aldrich Chemical toTETA diluted with water. For example, TETA was dissolved in 10 g ofwater. Then 10.6 g of polyphosphoric acid was added. The reactionproceeds vigorously and gives off much heat and vapor. The reactionproduct was dried in a vacuum oven directly, as not much water remained.More reactions were run utilizing 10 g H₂O, 10.8 g TETA, 18 gPolyphosphoric acid; 10 g H₂O, 10.3 g TETA, 17 g Polyphosphoric acid; 10g H₂O, 10.9 g TETA, 13 g Polyphosphoric acid; 10 g H₂O, 10.4 g TETA, 16g Polyphosphoric acid; and 10 g H₂O, 10.3 g TETA, 16.9 g Polyphosphoricacid. All six products were much more thermally stable than EDAP whenheated at 250° C. in a vacuum oven. The above reactions could be donewithout water with proper control of heat.

In this example, a mixture of melamine polyphosphate with the TETA saltof polyphosphoric acid is prepared. First, add 5 grams of melamine to 30g of water and heat to about 80° C. Then add about 18 g ofpolyphosphoric acid and react for about 15 minutes at which time somemelamine polyphosphate will be made. Then, add TETA to bring the mixtureto near neutral pH. React mixture fully. Then, dry in a vacuum oven.Other amines such as urea, guanidine, and dicyandiamide could be used inplace of melamine.

Dow Chemical Company makes EDA and ethyleneamines consisting of mixtureswith high boiling points that should work well according to the teachingof this patent. For example Dow Chemical sells a product calledtetraethylenepentamine-UHP which is a mixture of four differentpentamines and additional higher and lower molecular weightethyleneamines and their analogues, all with similar boiling pointsincluding linear, branched and two cyclic pentamines.

Another high boiling point Dow product is heavy polyamine X (HPA-X)which is a complex mixture of linear, branched, and cyclicethyleneamines, the structure of which can be deduced from the chemistryof manufacture and a knowledge of the structures present in TETA andTEPA.

1. A flame retardant composition prepared by a method of either (a)reacting ethylene diamine with polyphosphoric acid, or (b) reacting anethyleneamine or a mixture of ethyleneamines with polyphosphoric acid;in which the ratio of the polyphosphoric acid to the ethylene diamine,the ethyleneamine, or the mixture of ethyleneamines is such that a 10%solution of the flame retardant composition in water has a pH of 2.02 to6.5, and the ethyleneamine has three or more nitrogen atoms; in whichthe method additionally comprises the step of purifying thepolyphosphoric acid by ion exchange.
 2. The flame retardant compositionof claim 1 in which in which the method comprises the step (a).
 3. Aflame retardant composition prepared by a method of reacting anethyleneamine or a mixture of ethyleneamines with polyphosphoric acid;in which the ratio of the polyphosphoric acid to the ethyleneamine orthe mixture of ethyleneamines is such that a 10% solution of the flameretardant composition in water has a pH of 2.02 to 6.5, and theethyleneamine has three or more nitrogen atoms.
 4. The flame retardantcomposition of claim 1 in which the method additionally comprises thestep of heating the flame retardant composition at a temperature fromabout 60° C. to about 340° C. for less than 60 minutes under vacuum ofless than 30 inches of Hg.
 5. A flame retardant composition prepared bya method of either (a) reacting ethylene diamine with polyphosphoricacid, or (b) reacting an ethyleneamine or a mixture of ethyleneamineswith an acid selected from the group consisting of phosphoric acid,polyphosphoric acid, pyrophosphoric acid, and mixtures thereof; in whichthe ratio of the acid or acid mixture to the ethylene diamine, theethyleneamine, or the mixture of ethyleneamines is such that a 10%solution of the flame retardant composition in water has a pH of 2.02 to6.5, and the ethyleneamine has three or more nitrogen atoms; in whichthe method additionally comprises the steps of pellitizing the flameretardant composition into particles of at least 30 microns in diameteron average.
 6. A flame retardant containing composition comprising: a)30 to 99.75 percent by weight of a polymer; and b) 0.25 to 70 percent byweight of a flame retardant, the flame retardant prepared by a method ofeither (a) reacting ethylene diamine with polyphosphoric acid, or (b)reacting an ethyleneamine or a mixture of ethyleneamines withpolyphosphoric acid; in which the ratio of the polyphosphoric acid tothe ethylene diamine, the ethyleneamine, or the mixture ofethyleneamines is such that a 10% solution of the flame retardantcomposition in water has a pH of 2.02 to 6.5, and the ethyleneamine hasthree or more nitrogen atoms; in which the method additionally comprisesthe step of purifying the polyphosphoric acid by ion exchange.
 7. Theflame retardant containing composition of claim 6 in which in which themethod comprises the step (a).
 8. A flame retardant containingcomposition comprising: a) 30 to 99.75 percent by weight of a polymer;and b) 0.25 to 70 percent by weight of a flame retardant, the flameretardant prepared by a method of either (a) reacting ethylene diaminewith polyphosphoric acid, or (b) reacting an ethyleneamine or a mixtureof ethyleneamines with an acid selected from the group consisting ofphosphoric acid, polyphosphoric acid, pyrophosphoric acid, and mixturesthereof; in which the ratio of the acid or acid mixture to the ethylenediamine, the ethyleneamine, or the mixture of ethyleneamines is suchthat a 10% solution of the flame retardant composition in water has a pHof 2.02 to 6.5, and the ethyleneamine has three or more nitrogen atoms;in which the method additionally comprises the step of reacting theethylene diamine with formaldehyde and melamine before reacting theethylene diamine with the acid.
 9. A flame retardant containingcomposition comprising: a) 30 to 99.75 percent by weight of a polymer;and 0.25 to 70 percent by weight of a flame retardant, the flameretardant prepared by a method of reacting an ethyleneamine or a mixtureof ethyleneamines with polyphosphoric acid; in which the ratio of thepolyphosphoric acid to the ethyleneamine or the mixture ofethyleneamines is such that a 10% solution of the flame retardantcomposition in water has a pH of 2.02 to 6.5, and the ethyleneamine hasthree or more nitrogen atoms.
 10. A flame retardant containingcomposition comprising: a) 30 to 99.75 percent by weight of a polymer;and b) 0.25 to 70 percent by weight of a flame retardant, the flameretardant prepared by a method of either (a) reacting ethylene diaminewith polyphosphoric acid, or (b) reacting an ethyleneamine or a mixtureof ethyleneamines with an acid selected from the group consisting ofphosphoric acid, polyphosphoric acid, pyrophosphoric acid, and mixturesthereof; in which the ratio of the acid or acid mixture to the ethylenediamine, the ethyleneamine, or the mixture of ethyleneamines is suchthat a 10% solution of the flame retardant composition in water has a pHof 2.02 to 6.5, and the ethyleneamine has three or more nitrogen atoms;additionally comprising about 0.25 to 1%, relative to the weight of theflame retardant containing composition, of an anti drip agent; and 4.0to 30%, relative to the weight of the flame retardant containingcomposition, of a compound selected from the group consisting ofmelamine, melamine phosphate, melamine pyrophosphate, and mixturesthereof.
 11. The flame retardant containing composition of claim 10 inwhich the polymer is a thermoplastic polymer selected from the groupconsisting of polyesters, synthetic aliphatic or aromatic polyamides,polyolefins, polycarbonates, polyvinyl chloride, copolymers of vinylchloride, polyvinyl acetate, polystyrenics, polyacrylates,polycarbonates, polyphenoloxide, and ethylene vinyl acetates.
 12. Theflame retardant containing composition of claim 10 in which the polymeris selected from the group consisting of polyethylene, ethylenecopolymers, polypropylene, propylene copolymers,acrylonitrile-butadiene-styrene, methacrylic acid ionomers, andpolystyrene.
 13. The flame retardant containing composition of claim 10in which the polymer is selected from the group consisting ofpolypropylene, propylene copolymers, polyethylene, and ethylenecopolymers.
 14. A flame retardant composition prepared by a methodcomprising the steps of: a) reacting ethylene diamine, an ethyleneamine,or a mixture of ethyleneamines with formaldehyde and melamine, b)reacting the product of step a) with an acid selected from the groupconsisting of phosphoric acid, polyphosphoric acid, pyrophosphoric acid,and mixtures thereof; in which the ratio of the acid or acid mixture tothe ethylene diamine, the ethyleneamine, or the mixture ofethyleneamines is such that a 10% solution of the flame retardantcomposition in water has a pH of 2.02 to 10.5, and the ethyleneamine hasthree or more nitrogen atoms.
 15. The flame retardant composition ofclaim 14 in which the method additional comprises the step of: c)heating the product of step b) at a temperature of about 60° C. to about340° C. for less than 60 minutes under vacuum of less than 30 inches ofHg to form the flame retardant composition.
 16. The flame retardantcomposition of claim 14 in which step a) is the step of reactingethylene diamine with polyphosphoric acid.
 17. The flame retardantcomposition of claim 4 in which the method comprises the step (b). 18.The flame retardant composition of claim 17 in which the ethyleneamineor mixture of ethyleneamines is selected from the group consisting ofdiethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylene hexamine, and mixtures thereof.
 19. The flame retardantcontaining composition of claim 6 in which the composition additionallycomprises 0.25 to 1%, relative to the weight of the flame retardantcontaining composition, of an antidrip agent.
 20. The flame retardantcontaining composition of claim 19 in which the method comprises thestep (a).
 21. The flame retardant composition of claim 5 in which themethod comprises the step (a).
 22. The flame retardant composition ofclaim 3 in which the method additionally comprises the step of purifyingthe polyphosphoric acid by ion exchange.
 23. The flame retardantcontaining composition of claim 9 in which the method additionallycomprises the step of purifying the polyphosphoric acid by ion exchange.24. The flame retardant containing composition of claim 6 in which theflame retardant composition is a molecular dispersion.
 25. The flameretardant containing composition of claim 24 in which the polymer ispolypropylene or polyethylene.